Garage roof insulation

[brooklyn07]

Hi All

I have recently moved into a house that came with a detached garage. I am turning this into my office which will contain several PC's, and printers and some other machinery.

I also plan to having some form of heating in there as it will be occupied for around 12 hours a day.

Anyway, it currently has a flat fibreglass roof with no insulation at all. I bought 100mm cellotex to shove up in there, but then i realised theres no ventilation in the garage at all.

The joists run from left to right so ventilation front to back is not an option and the garage is actually built up against next doors garage so i wouldn't be able to put the ventilation from left to right either.

I've read various articles that say don't worry about ventilation, just shove the 100mm cellotex in between the joists right up against the OSB and then put a vapour barrier underneath, followed by plasterboard.

However, i know this isn't the "proper" way to do it, but i don't see how else i'm going to ventilate it. Is this way going to work or am i going to end up with rotten timbers in 5 years?

Second problem, if i do somehow manage to ventilate it then i'd have to drop the cellotex down by 50mm and then there won't be enough room for the downlights I planned on having because i'd have to cut a chunk through the cellotex and cut through the vapour barrier, which i've read is bad idea.

Any ideas please?

 

[freddiemercurystwin]

On various garage conversions in the past when ventilation has not been an option or impracticable Building Control have accepted just getting insulation up against the underside of the deck. It's not ideal but as you say not much else you can do, see if your BCO will accept it.

 

[brooklyn07]

Thanks. Is there a reason why i need to inform BC on an existing garage? Its not really a garage conversion (and its not attached to the house) so do the BC rules still apply?

 

[freddiemercurystwin]

It sounds like a garage conversion, habitable room with heating etc so would need building regs approval, though many don't bother. The regs (even if you don't bother with approval) are generally pretty straightforward and halp to ensure you end up with a useable space and good quality.

 

[Murdochcat]

Our neighbours have a garage that is attached to the other neighbours.

They converted the back half of theirs to an office and needed full planning and labc involved